1. Field of the Invention:
The present invention relates to a process for the manufacture of vinyl chloride by the reaction of acetylene with hydrogen chloride.
2. Discussion of the Background:
The large-scale manufacture of vinyl chloride by the reaction of acetylene with hydrogen chloride is conventionally conducted in the gas phase in the presence of a heterogeneous HgCl.sub.2 -containing catalyst. For ecological reasons a substantial interest exists in employing a catalyst which is free of mercury chloride. However, alternative proposals for a gas phase process have failed to achieve success.
It is pointed out that some examples of the hydrochlorination of acetylene in the liquid phase are known and are described in the literature. These methods, however, are impracticable on a large scale. Thus, it is known, as described in U.S. Pat. Nos. 1,812,542; 1,934,324 and 3,113,158 that acetylene can be converted into vinyl chloride by reaction with aqueous hydrochloric acid in a reaction medium containing a dissolved copper compound, preferably dissolved copper chloride as a catalyst. In the process of U.S. Pat. No. 1,812,542 the catalyst solution in addition contains ammonium chloride, while the process described in U.S. Pat. No. 1,934,324 utilizes an alkali metal or alkaline earth metal chloride in the reaction medium. U.S. Pat. No. 3,113,158 describes a phosphine and/or diphosphine and/or methyl phosphine as present in the reaction medium.
Russian Patent No. 165,446 describes the hydrochlorination of acetylene in the presence of copper chloride in dimethylformamide as a solvent, while Russian Patent No. 232,956 describes the reaction as occurring in the presence of copper chloride in a triethanolamine solution acidified with hydrochloric acid.
The available literature describe acetylene conversions ranging from 26 to 99%. Space-time yields defined as ##EQU1## of 10 to 130 g vinyl chloride/l.multidot.h are typically reported. Further, the high concentrations of up to 60% by weight of copper chloride in the solvent are high and are a disadvantage. Another drawback of the conventional catalyst systems is that they usually contain additional components.
Japanese Laid Open application 77/136,103 discloses a process for the manufacture of vinyl chloride from acetylene and hydrogen chloride in the presence of gold chloride and platinum chloride and/or palladium chloride as catalyst. Water or organic solvents such as paraffins, chlorinated hydrocarbons, diisopropylbenzene, chloralhydrate and ethylene chlorohydrin are used as solvents or suspending media. The catalytically active metal chloride can also be suspended on a carrier such as activated charcoal. The reference further discloses the use of a transition metal chloride as an additional catalyst component. Conversion of 54 to 74% with selectivities of about 99% are attained. The space-time yield amounts to about 100 g vinyl chloride/l.multidot.h. A drawback of the process described is that at least two different noble metal chlorides must be present and that only low conversion rates are attained. A need therefore continues to exist for an improved reaction system for the hydrochlorination of acetylene to vinyl chloride.